Bone marrow transplantation procedure has emerged as an effective treatment for hematological malignancies. However, recurrence of leukemia is still the major cause of treatment failure. Subsequent treatment in this category of patients, generally considered incurable, has not been yet standardized. At our institution, 13 patients, 7 with acute non lymphoid leukemia (ANLL) and 6 with acute lymphoid leukemia (ALL), were treated at relapse after bone marrow transplantation either autologous or allogeneic (AuBMT 8, ABMT 4) performed in complete remission (CR). The interval between BMT and relapse was less than 9 months in 6 patients (2 ABMT and 4 AuBMT) and more than 9 months in 7 patients. Early relapsed patients showed no response to treatment and died at a median of 5.5 months (range 1-13) after relapse. Late relapse after BMT was characterized by a high percentage of response (5 CR and 1 PR), particularly after intensive chemotherapy and by a longer survival (median 14 months; range 2-36). Chemotherapy after transplantation should be carefully evaluated in patients relapsed after BMT in order to select a population that can achieve long term disease free survival.